1. Field
The embodiments relate to a fusing device for an image forming apparatus. More particularly, the embodiments relate to an electromagnetic induction heating type fusing device.
2. Description of the Related Art
Generally, a fusing device used in an image forming apparatus is constituted to have a halogen lamp that is arranged in an inner space within a metallic fusing roller and heats the fusing roller. However, the fusing device using this heating method consumes a large amount of energy when rapidly heating and it takes a long time for the fusing device to heat up the fusing roller to a fusing temperature. To overcome these drawbacks, fusing devices using an electromagnetic induction heating method have been developed and used.
The electromagnetic induction heating type fusing device generally uses an outer electromagnetic induction heating type fusing device that is configured to have a thin fusing roller or a thin heating belt and an induction heating member disposed outside the fusing roller or the heating belt so as to heat the fusing roller or the heating belt by an electromagnetic induction from the outside of the fusing roller or the heating belt. In the outer electromagnetic induction heating type fusing device (hereinafter referred to as an IH fusing device), a coil to generate a magnetic flux is arranged outside a heated member, such as a fusing roller or a heating belt, etc, and a ferrite core to guide the magnetic flux to the heated member is arranged outside the coil. A sectional area of the coil is determined by a size of the magnetic flux that can sufficiently heat the heated member until a predetermined time. Also, since the coil is arranged to be spaced apart a predetermined distance from the heated member, for securing a necessary heating sectional area it is required to reduce a thickness of the coil in a sectional direction thereof so that the coil has a large wiring angle with respect to the heated member. Here, the wiring angle of the coil presents an angle between two lines that join a center point of the heated member and opposite side ends of the coil.
According to a configuration of the outer electromagnetic induction heating type fusing device, because the wiring angle of the coil wound around a surface facing the heated member should be over a predetermined angle, it is difficult to reduce a diameter of the heated member. Further, for preventing temperature of the opposite ends of the heated member from lowering, it is required that the coil is formed to cover a size larger than a width of a printing medium in a length direction of the heated member. Therefore, there is a problem that the fusing device is formed in a large size.